1. Field of the Invention
The present invention relates to an apparatus for measuring and analyzing a concentration or a weight of particulates included in an exhaust gas from a diesel engine, in particular a high-temperature exhaust gas exhausted from a diesel engine and then diluted and cooled with air having a room temperature.
2. Description of the Prior Art
It has been known that particulates included in low-temperature exhaust gas consist of DS (dry soot), which is a substance insoluble in organic solvents (for example dichlormethane), and SOF (soluble organic fractions), which is a substance soluble in organic solvents. Of these substances, the former, that is to say DS, is mainly formed of agglomerated spherical carbon particles having a crystalline structure and generally observed as a black smoke since they are turned black in color, while the latter, that is to say SOF, consists of drops of condensed hydrocarbon and lubricating oil as a preceding-stage substance of soot and generally observed as a white smoke or a blue smoke since it turns white or blue in color after being exhausted.
That is to say, carbon particles and gaseous hydrocarbon compounds (including high boiling point hydrocarbon compounds and low boiling point hydrocarbon compounds) are contained in a high-temperature exhaust gas immediately after being exhausted from a diesel engine. Upon diluting and cooling this high-temperature exhaust gas exhausted from the diesel engine with air having a room temperature, the high boiling point hydrocarbon compounds are condensed to turn into fine liquid drops, thereby forming the SOF, which generates the particulates together with DS generated from said carbon particles.
Accordingly, the concentration or the weight of high boiling point hydrocarbon compounds in the high-temperature exhaust gas immediately after being exhausted from the diesel engine always shows a high correlation with the concentration or weight of the SOF. In addition, particulates consisting of DS and SOF and the low boiling point hydrocarbon compounds, which remain in the gaseous form, are contained in a low-temperature exhaust gas exhausted from the diesel engine and then diluted and cooled with air having a room temperature.
However, since the particulate exhaust characteristics, in short the concentrations or the weights of DS and SOF constituting said particulates, are remarkably varied in dependence upon the operating conditions such as load, rotation speed and the like of the engine, it is important for the attainment of fundamental data indicative of an improvement in the particulate exhaust characteristics of the engine to not only determine a total concentration or a total weight of particulates exhausted, but also individually determine the concentration or the weight of DS and SOF.
Previously, measurements and analyses of these particulates have been carried out by using the following filter-weighing method:
An exhaust gas from a diesel engine is filtered to sample particulates (DS and SOF) contained in the exhaust gas onto a filter, and then the sample is subjected to a particulate extraction treatment to dissolve SOF in organic solvents (for example dichlormethane) and leave DS on the filter, and then the weight of the remainder (SOF) left after heating and vaporizing said organic solvents is measured by means of a balance. The weight of the substance (DS) trapped on said filter insoluble in the organic solvents is also measured by means of the balance.
However, the above described conventional method takes a very long time for the measurement and the analysis to be completed since it usually takes about 8 hours for the extraction of SOF. This method also has the disadvantages of requiring a remarkably complicated manual measuring and analyzing procedure, and only an intermittent measurement and analysis can be carried out.